Evaluation of the AgDISP aerial spray algorithms in the AgDRIFT model

Abstract

A systematic evaluation of the AgDISP algorithms, which simulate off-site drift and deposition of aerially applied pesticides, contained in the AgDRIFT model was performed by comparing model simulations to field-trial data collected by the Spray Drift Task Force. Field-trial data used for model evaluation included 161 separate trials of typical agriculture aerial applications under a wide range of application and meteorological conditions. Input for model simulations included information on the aircraft and spray equipment, spray material, meteorology, and site geometry. The model input datasets were generated independently of the field deposition results, i.e., model inputs were in no way altered or selected to improve the fit of model output to field results. AgDRIFT shows a response similar to that of the field observations for many application variables (e.g., droplet size, application height, wind speed). However, AgDRIFT is sensitive to evaporative effects, and modeled deposition in the far-field responds to wet bulb depression whereas the field observations did not. The model tended to overpredict deposition rates relative to the field data for far-field distances, particularly under evaporative conditions. AgDRIFT was in good agreement with field results for estimating near-field buffer zones needed to manage human, crop, livestock, and ecological exposure.

A library of forest canopy structure for use in interception modeling

“…The canopy algorithm as described above has been inserted into the spray interception model programmed into AGDISP (Teske et al, 2003), a validated predictive model for the dispersal and deposition of spray material released from aircraft (Bird et al, 2002). In the test scenario the spray originated at 35.75 m, 10 m above the height of the generic deciduous canopy.…”

The OML-SprayDrift model for predicting pesticide drift and deposition from ground boom sprayers

“…This type of measurement can be difficult to perform properly in order to measure the far-field drift deposition of small droplets using smooth horizontal surfaces, such as alphacellulose sheets, on a rough field surface. 8,11) To avoid this problem, this study measured the vertical profile of the horizontal drift. In the far field, the total amount of collected spray drift will be much larger than the horizontally deposited spray drift measured per unit area, which reduces uncertainty in measurements.…”

“…Before calibration and validation, all measurements were normalized to the same application rate, i.e., 300 L ha Table 1). The calculated meteorological data during the individual trails are based on 10-min averages in correspondence with Bird et al 8) Measurements were performed for five spray tracks parallel to the hedgerow with an increasing distance from the hedgerow (cf. Spray drift was collected using commercial plastic hair curlers (M-cosmetics, Denmark) mounted on masts 0.5, 1, 2, and 4 m above the ground.…”

“…However, the main concern has been habitats with no significant vertical component, e.g., water bodies. Different types of model approaches have been taken all with advantages and disadvantages: Computational Fluid Dynamics (CFD) models, 4) random-walk trajectory models, [5][6][7][8][9] diffusionadvection models, 10) and Gaussian tilting plume models. 11,12) CFD models can calculate the complicated flow and dispersion close to nozzles and spray equipment.…”

“…11) These models either do not take atmospheric stability into account [6][7][8] or are calibrated to a particular atmospheric situation. 9) In addition, some models disregard the effects of evaporation of the droplets.…”